JP4943671B2 - Lower hydrocarbon aromatization catalyst and method for producing aromatic hydrocarbon and hydrogen from lower hydrocarbon using the same - Google Patents

Abstract

A high-conversion, high-selectivity catalyst with which an aromatic hydrocarbon, e.g., benzene or naphthalene, and hydrogen are produced from a lower hydrocarbon, e.g., natural gas; and a method of aromatizing a lower hydrocarbon with the catalyst. The catalyst for the aromatization of a lower hydrocarbon comprises (a) a catalytst material comprising at least one member selected from the group consisting of molybdenum and compounds thereof and (b) a carrier comprising a porous metallosilicate, and is characterized by having at least macropores having a pore diameter of 100 nm or lager. By the method of lower hydrocarbon aromatization with the catalyst, an aromatic hydrocarbon and hydrogen can be obtained from a lower hydrocarbon with a high conversion and high selectivity.

Description

  The present invention relates to an aromatic hydrocarbon and hydrogen gas mainly composed of benzenes and naphthalenes, which are useful as raw materials for chemical products such as chemical industry, chemicals, and plastics from gases containing lower hydrocarbons such as natural gas. And a method for producing an aromatic hydrocarbon and hydrogen by subjecting a lower hydrocarbon to a high temperature catalytic reaction in the presence of the catalyst.

  Conventionally, aromatic hydrocarbons such as benzene, toluene and xylene are mainly produced from naphtha. In addition, as a method for producing naphthalenes, non-catalytic methods such as a solvent extraction method from coal and the like, a gas pyrolysis method of natural gas, acetylene and the like are employed. However, in these conventional methods, only a few percent of benzene and naphthalenes can be obtained with respect to raw materials such as coal and acetylene, and a large amount of by-products such as aromatic compounds, hydrocarbons, tar, and insoluble carbon residues are present. It had the problem of containing. Further, the solvent extraction method has a problem that a large amount of an organic solvent is required. In addition, in the case of gas pyrolysis, the production of naphthalenes with a conversion efficiency of several percent or more requires a reaction temperature of 1000 ° C. or higher, but the yield of naphthalene is less than several percent of the converted methane or acetylene. There was also a problem that there was, there was a problem in practical use.

  In addition, as a method for producing naphthalenes using a catalyst, a method for producing naphthalenes by dehydrocondensation reaction of alkylbenzenes such as orthoxylene at a high temperature using a platinum-supported catalyst is also known. However, the conversion efficiency of naphthalenes is low, and alkylbenzenes used as raw materials are expensive, causing problems in practical use.

  Furthermore, the method for producing the hydrogen gas co-produced in the present invention includes a water gas shift reaction using carbon monoxide produced by iron oxide waste gas or coal partial oxidation, and a natural gas steam reforming reaction. There are industrial processes carried out under high temperature and high pressure reaction conditions. In addition, there are hydrogen production methods such as thermal cracking of crude oil. The production gas contains sulfur and nitrogen oxides, which are catalyst poisons, and carbon monoxide, which is a by-product, in the produced hydrogen. Therefore, in the case of hydrogen gas produced by these conventional methods, there has been an industrial problem that requires a large load and equipment for removal and purification of the catalyst poison. Further, these conventional hydrogen production methods have a serious problem in terms of environmental problems because a large amount of carbon dioxide is discharged as a by-product as hydrogen is produced.

  On the other hand, as a method of co-producing lower hydrocarbons, especially aromatic hydrocarbons such as benzene from methane and hydrogen, in the presence of a molybdenum catalyst supported on ZSM-5, in a system without oxygen or oxidant, A method of reacting methane is known (see, for example, Non-Patent Document 1). However, when these catalysts are used, there are problems that carbon deposition is large and that the conversion rate of methane is low.

  In the examples, lower hydrocarbons are efficiently converted into aromatic hydrocarbons by a catalyst in which a catalyst material such as molybdenum is supported on a porous metallosilicate having a pore diameter of 7 angstroms (angstroms) in the examples. Thus, it has been confirmed that high-purity hydrogen can be obtained (see, for example, Patent Documents 1 and 2). However, even with these catalysts, the production efficiency of aromatic hydrocarbons and hydrogen was still low.

  Under such circumstances, it has been desired to develop a catalyst excellent in reaction efficiency that further increases the production efficiency of aromatic hydrocarbons and hydrogen and maintains stable performance for a long period of time.

"JOURNAL OF CATALYSIS", pages 165, 150-161 (1997) JP 10-272366 A Japanese Patent Laid-Open No. 11-60514

  In view of the actual situation and problems of the prior art, the present invention uses a lower hydrocarbon mainly composed of methane such as natural gas to convert aromatic hydrocarbons such as benzene and naphthalene and hydrogen gas into a high conversion rate and high. Provided is a lower hydrocarbon aromatization catalyst which can be produced simultaneously at a selectivity and which exhibits stable catalytic activity for a long time, and a method for producing aromatic hydrocarbons and hydrogen from lower hydrocarbons using the same. This is the issue.

  In order to achieve the above object, the present inventors have intensively studied, and as a result, have completed the present invention.

  That is, the lower hydrocarbon aromatization catalyst of the present invention comprises (a) at least one selected from the group consisting of molybdenum or a compound thereof as a catalyst material, and (b) a porous metallosilicate as a support. A lower hydrocarbon aromatization catalyst comprising at least macropores having a pore diameter of 100 nm or more.

  The lower hydrocarbon aromatization catalyst of the present invention also comprises (a) at least one selected from the group consisting of molybdenum or a compound thereof as a catalyst material, and (b) a lower metal comprising a porous metallosilicate as a support. A hydrocarbon aromatization catalyst, characterized in that the catalyst has a total pore volume of at least 0.25 ml / g or more.

  The lower hydrocarbon aromatization catalyst of the present invention also comprises (a) at least one selected from the group consisting of molybdenum or a compound thereof as a catalyst material, and (b) a lower metal comprising a porous metallosilicate as a support. A hydrocarbon aromatization catalyst, characterized in that the volume of macropores having a pore diameter of 100 nm or more is at least 0.20 ml / g or more.

  The lower hydrocarbon aromatization catalyst of the present invention preferably further contains at least one selected from the group consisting of ruthenium, cobalt, rhodium or compounds thereof as a catalyst material.

  Moreover, the method for producing an aromatic hydrocarbon and hydrogen from the lower hydrocarbon of the present invention is characterized by using the above catalyst as a catalyst.

  According to the catalyst of the present invention, it is possible to simultaneously produce aromatic hydrocarbons and hydrogen from lower hydrocarbons with high conversion and high selectivity.

  In addition, when the aromatic hydrocarbon and hydrogen are produced from the lower hydrocarbon using the catalyst of the present invention, not only the reaction conversion of the lower hydrocarbon can be improved but also benzene, toluene, naphthalene, etc. Since it is possible to suppress the decrease in the production rate of aromatic hydrocarbons and hydrogen, it is possible to produce aromatic hydrocarbons and hydrogen with high activity and high yield, and for a long time, stable catalytic ability. Can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with specific examples.

  The aromatization catalyst of the present invention is characterized by having macropores having a pore diameter of 100 nm or more. Macropores generally mean pores of about 50 nm to about 1000 nm (see Catalyst Dictionary, Yoshio Ono, Makoto Misono, edited by Yoshihiko Morooka, Asakura Shoten), and macropores of 100 nm or more By substantially pores of 100 nm to about 1000 nm are meant.

  The aromatization catalyst of the present invention is also characterized in that the total pore volume is at least 0.20 ml / g or more, and the total pore volume is preferably 0.3 to 0.8 ml / g. Good to have.

  Presence of macropores of 100 nm or more and a total pore volume of 0.25 ml / g or more make it difficult for the deposited carbon to block the pores, and at the same time, the reaction gas enters the catalyst pores. This increases the gas diffusion efficiency and improves the reactivity. Thus, not only the reaction activity but also the performance degradation due to the precipitated carbon can be suppressed, and a stable catalytic ability can be obtained for a long time. If only pores having a pore diameter of less than 100 nm are present, the efficiency of gas diffusion into the catalyst is lowered, and the reactivity is significantly lowered, which is not preferable. Further, if the total volume of the pore volume is less than 0.25 ml / g, clogging with carbon precipitated by side reaction is likely to occur, leading to performance deterioration, which is not preferable. On the other hand, if the pore volume is larger than 0.8 ml / g, the crushing strength of catalyst pellets and the like is lowered, which is not preferable for practical use.

  Therefore, when the aromatization catalyst of the present invention has a pore volume of macropores of 100 nm or more, particularly 0.20 ml / g or more, preferably 0.3 to 0.5 ml / g, gas diffusion into the catalyst The efficiency is particularly preferable, and the reactivity is remarkably increased, which is very preferable.

  For example, in the case of an aluminosilicate, the metallosilicate used in the aromatization catalyst of the present invention is a molecular sieve 5A (UTA), a faujasite (NaY) and NaX, ZSM-5, which are porous bodies composed of silica and alumina, A zeolite carrier characterized by comprising a micropore or channel of 0.6 nm to 1.3 nm in a porous carrier such as H-ZSM-5, ALPO-5, VPI-5 mainly composed of phosphoric acid, Examples include mesoporous porous carriers such as FSM-16 and MCM-41 characterized by cylindrical pores (channels) of mesopores (1 nm to 10 nm) containing silica as a main component and partly alumina as a component. it can.

The metallosilicate used in the aromatization catalyst of the present invention also has a surface area of 200 to 1000 m ² / g, and its micro and mesopores are preferably in the range of 0.5 nm to 10 nm. When the metallosilicate is, for example, aluminosilicate, the silica / alumina content ratio of silica / alumina, which is usually available, can be used as the content ratio of silica and alumina. In order to carry out the hydrogen aromatization reaction at a practical lower hydrocarbon conversion and selectivity to aromatic hydrocarbon, the silica / alumina ratio is preferably 10-100.

  The catalyst of the present invention can be obtained by supporting a precursor containing molybdenum on a metallosilicate.

  Examples of precursors containing molybdenum include ammonium paramolybdate, phosphomolybdic acid, 12 silicomolybdic acid, halides such as chlorides and bromides, mineral salts such as nitrates, sulfates and phosphates, Examples thereof include carboxylates such as carbonates, acetates and oxalates.

  As a method of supporting molybdenum on a metallosilicate, a method of impregnating and supporting an aqueous solution of the above-described precursor containing molybdenum on a metallosilicate support or by supporting it by an ion conversion method and then heat-treating in air is common. It is. More specifically, for example, the metallosilicate carrier is impregnated and supported with an aqueous solution of ammonium molybdate, dried, and then heat-treated in an air stream at 250 to 800 ° C, preferably 350 to 600 ° C. Thus, a metallosilicate catalyst supporting molybdenum can be produced.

  When molybdenum is supported on a metallosilicate support, the weight ratio of molybdenum to the support is 0.001 to 50%, preferably 0.01 to 40%, which is a good support range.

  The catalyst of the present invention may support not only a precursor containing molybdenum but also a precursor containing at least one of ruthenium, cobalt, and rhodium on a metallosilicate.

  Examples of precursors containing at least one of ruthenium, cobalt, and rhodium include halides such as chlorides and bromides, mineral salts such as nitrates, sulfates, and phosphates, carbonates, acetates, Examples thereof include carboxylates such as oxalates.

  The weight ratio of at least one element of ruthenium, cobalt and rhodium to the support is 0.001 to 50%, preferably 0.01 to 40%, which is a good loading range.

  As a method for supporting at least one element of ruthenium, cobalt, and rhodium on a metallosilicate, an aqueous solution of these precursors described above is supported on a metallosilicate support by impregnation or ion conversion, and then in the air. A heat treatment method is common.

  The order of loading is (1) loading molybdenum, and then loading at least one element of ruthenium, cobalt, and rhodium. (2) loading at least one element of ruthenium, cobalt, and rhodium. Thereafter, molybdenum is supported, and (3) molybdenum and at least one element of ruthenium, cobalt, and rhodium are simultaneously supported, and any order may be used.

  More specifically, these supporting methods will be described. For example, after a metallosilicate support is impregnated with an aqueous solution of ammonium molybdate and dried, heat treatment is performed at 250 to 800 ° C., preferably 350 to 600 ° C. in an air stream. Then, after further impregnating and supporting an aqueous ruthenium nitrate solution and drying, heat treatment is performed at 250 to 800 ° C., preferably 350 to 600 ° C. in an air stream to produce a metallosilicate catalyst supporting molybdenum / ruthenium. Can do.

  The catalyst used in the present invention can be used by adding a binder such as silica, alumina, clay, etc., and molding it into pellets or extrudates. In this case, first, molybdenum and at least one element of ruthenium, cobalt, and rhodium can be supported on the metallosilicate and then molded for use. However, the metallosilicate serving as the carrier is in the form of pellets. Alternatively, molybdenum and at least one element of ruthenium, cobalt, and rhodium can be supported after being formed into an extruded product.

  In the present invention, the lower hydrocarbon means a hydrocarbon containing at least 50% by weight, preferably at least 70% by weight of methane, and other saturated and unsaturated hydrocarbons having 2 to 6 carbon atoms. . Examples of these saturated and unsaturated hydrocarbons having 2 to 6 carbon atoms include ethane, ethylene, propane, propylene, n-butane, isobutane, n-butene and isobutene.

  In the method for producing aromatic hydrocarbons and hydrogen from the lower hydrocarbons of the present invention, the aromatization reaction of the lower hydrocarbons can be carried out in a batch-type or flow-type reaction mode. Or it is preferable to implement by the flow-type reaction formats, such as a fluidized bed. The reaction is preferably carried out by contacting the lower hydrocarbon raw material with the catalyst in the gas phase in the absence of oxygen at 300 to 800 ° C., preferably 450 to 775 ° C. The reaction is suitably carried out at 0.01 to 1 MPa, preferably 0.1 to 0.7 MPa. The weight hourly space velocity (WHSV) is 0.1 to 10, preferably 0.5 to 5.0. Unreacted raw material recovered from the reaction product can be recycled to the aromatization reaction.

Furthermore, the method for producing aromatic hydrocarbons and hydrogen from the lower hydrocarbons of the present invention shortens the induction period for producing aromatic hydrocarbons, so that hydrogen gas, hydrazine, metal hydrogen compounds such as BH ₃ , NaH Further, a catalyst activation process including a pretreatment with AlH ₃ or the like may be performed.

  Hereinafter, the present invention will be described in more detail by way of examples.

As a metallosilicate support, 390 g of 25% silica sol and 300 g of ion-exchanged water were added to 900 g of H-ZSM-5, and after kneading sufficiently, extrusion molding of 2 mm was performed, followed by drying and firing to obtain a catalyst support. . 40 g of the obtained catalyst carrier was impregnated with an aqueous solution in which 4.85 g of ammonium molybdate was dissolved in 16.4 ml of ion-exchanged water, dried at 120 ° C. for 16 hours, and calcined at 550 ° C. for 4 hours to obtain a catalyst. . The pore volume of macropores of 100 nm or more of this catalyst was 0.39 ml / g. The silica / alumina ratio of H-ZSM-5 was 32, and the specific surface area was 320 m ² / g.

  55 g of the catalyst obtained in Example 1 was impregnated with an aqueous solution (9.8% as Ru) in which 7.7 g of ruthenium nitrate was dissolved in 15 ml of ion-exchanged water, dried at 120 ° C. for 16 hours, and at 550 ° C. for 4 hours. A catalyst was obtained by calcination. The pore volume of macropores of 100 nm or more of this catalyst was 0.38 ml / g.

  55 g of the catalyst obtained in Example 1 was impregnated with an aqueous solution obtained by dissolving 18 g of rhodium nitrate in 4.6 ml of ion-exchanged water (4.3% as Rh), dried at 120 ° C. for 16 hours, and 550 ° C. for 4 hours. A catalyst was obtained by calcination. The pore volume of macropores of 100 nm or more of this catalyst was 0.40 ml / g.

  55 g of the catalyst obtained in Example 1 was impregnated with an aqueous solution obtained by dissolving 2.2 g of cobalt nitrate in 23 ml of ion-exchanged water, dried at 120 ° C. for 16 hours, and calcined at 550 ° C. for 4 hours to obtain a catalyst. . The pore volume of macropores of 100 nm or more of this catalyst was 0.40 ml / g.

As a metallosilicate carrier, 390 g of 25% silica sol and 400 g of ion-exchanged water were added to 900 g of H-ZSM-5, and after kneading sufficiently, extrusion molding of 2 mm was performed, followed by drying and firing to obtain a catalyst carrier. . A catalyst was obtained by dissolving 4.85 g of ammonium molybdate in 16.4 ml of ion-exchanged water, impregnating the aqueous solution with 40 g of the support, drying at 120 ° C. for 16 hours, and calcining at 550 ° C. for 4 hours. The pore volume of macropores of 100 nm or more of this catalyst was 0.70 ml / g. The silica / alumina ratio of H-ZSM-5 was 32, and the specific surface area was 320 m ² / g.

Comparative Example 1

  As a metallosilicate carrier, 13 g of silica sol was added to 87 g of H-ZSM-5, and pellets were obtained by compression molding. The pellet was impregnated with an aqueous solution obtained by dissolving 12 g of ammonium molybdate in 17 ml of ion-exchanged water, and calcined at 550 ° C. for 10 hours to obtain a catalyst. The pore volume of macropores of 100 nm or more of this catalyst was 0.10 ml / g.

Test example

  Using the catalysts obtained in Examples 1 to 5 and Comparative Example 1, tests for producing aromatic hydrocarbons and hydrogen from lower hydrocarbons were conducted, and the performance of the catalysts was confirmed. The performance index used here was the number of each product produced in 1 second per gram of the catalyst, that is, nmol number of hydrogen and aromatic hydrocarbon.

  All the reaction tests were performed under the conditions of a methane reaction temperature of 750 ° C., a pressure of 0.3 MPa, and a weight hourly space velocity (WHSV) of 2,700 ml / g / h. The composition of the reaction gas used as the lower hydrocarbon raw material is 90% methane and 10% argon.

  In the pretreatment of the catalyst, the catalyst was heated to 550 ° C. under an air stream and maintained for 1 hour, then switched to the reaction gas, heated to 650 ° C. and maintained for 1 hour. Then, it heated up to 750 degreeC, activity evaluation was performed, and the performance of the catalyst was confirmed.

  In the analysis, hydrogen, argon, and methane were analyzed by TCD gas chromatography. Benzene, toluene, xylene and naphthalene were analyzed by FID gas chromatography. The pore volume was measured by mercury porosimetry.

  As is clear from Table 1, in Comparative Example 1, the yields of benzene, toluene, naphthalene and hydrogen were low from the beginning of the reaction, and the yields of benzene, toluene, naphthalene and hydrogen were significantly reduced as the reaction time passed. . On the other hand, in Examples 1 to 5, the yields of benzene, toluene, naphthalene and hydrogen were remarkably high from the beginning of the reaction as compared with Comparative Example 1, and the decrease in the yield was relatively small even after the reaction time had elapsed.

Claims (5)

  (A) at least one selected from the group consisting of molybdenum or a compound thereof as a catalyst material, and (b) a lower hydrocarbon aromatization catalyst comprising porous metallosilicate as a carrier, A catalyst for aromatizing a lower hydrocarbon, characterized in that the volume of macropores having a pore diameter of 100 nm or more is at least 0.20 ml / g or more. As catalysts materials, ruthenium, cobalt, rhodium or catalyst according to claim 1 comprising at least one selected from the group consisting of those compounds. The catalyst according to claim 1 or 2 , further comprising ruthenium or a compound thereof as a catalyst material. The catalyst according to claim 1 or 2 , further comprising rhodium or a compound thereof as a catalyst material. A method for producing an aromatic hydrocarbon and hydrogen from a lower hydrocarbon, wherein the aromatic hydrocarbon and hydrogen are converted from the lower hydrocarbon using the catalyst according to any one of claims 1 to 4 as a catalyst. How to manufacture.